Offshore equipment and personnel transfer system



Aug. 27, 1968 R. P. VINCENT 3,398,845

QFFSHORE EQUIPMENT AND PERSONNEL TRANSFER SYSTEM 2 Sheets-Sheet 1 Filed Oct. 26, 1966 RENIC P. VINCENT INVENTOR.

ATTORNEY Aug. 27, 1968 R. P. VINCENT 3,398,845

OFFSHORE EQUIPMENT AND PERSONNEL TRANSFER SYSTEM Filed Oct. 26, 1966 2 Sheets-Sheet 2 I war EH Q J J lo] 200 -v\/AvEs FIG. 4.

RENIC P. VINCENT INVENTOR.

BY J, M

ATTORNEY United States Patent O 3,398,845 OFFSHORE EQUIPMENT AND PERSONNEL TRANSFER SYSTEM Renic P. Vincent, Tulsa, Okla., assignor to Pan American Petroleum Corporation, a corporation of Delaware Filed Oct. 26, 1966, Ser. No. 589,548 2 Claims. (Cl. 214-152) ABSTRACT OF THE DISCLOSURE This concerns a method for transferring objects between a floating vessel on a body of water and a fixed platform having a working deck supported above the body of water. A transfer line is connected at one end to the top of a derrick supported above a platform and the other end of the transfer line is anchored to the floor of the body of water at a distance of about 2,000 feet or more. A floating vessel having a swivel fork means supported above a superstructure is maneuvered to engage the transfer line between the platform and its anchor. The floating vessel is moved outwardly until the transfer line is held in firm contact with the fork. Then objects are transferred along the line between the floating vessel and the platform.

This invention relates to the transfer of equipment and personnel at offshore locations. It especially relates to the transfer between a floating cargo vessel and a working platform, such as a floating drilling vessel, supported above the surface of a body of water and used for marine drilling operations.

Briefly, the invention in a preferred embodiment includes a transfer line connecting an anchor member placed in the bottom of the body of water and a working or drilling platform located above the surface of the water. A cargo ship is provided with a special swivel fork which extends above its superstructure. The cargo ship moves under the line and picks up the cable or transfer line with the swivel fork. The cargo vessel then moves outwardly until the overhead transfer line is in firm contact with the fork. Cargo is then transferred between the cargo vessel and the working platform by use of traveling blocks along the overhead line. Various embodiments and modifications of this will be discussed hereinafter.

The search for petroleum has, in recent years, led to exploration in marine environments such as the Gulf of Mexico, the Persian Gulf, and the Cook Inlet in Alaska. When wells are drilled in such environments, they are drilled either from a fixed platform or a floating platform. In either instance, a working deck for supporting a drilling derrick and associated equipment is supported above the surface of the body of water. In the fixed platform, it is customary to drive piles into the bottom of the body of water and support the platform from such piles. This has been done successfully in water up to 100 or more feet. In deeper water it is normally more advantageous to use a fioating drilling vessel or barge to support the working deck and drilling equipment. Various means are known to maintain the floating drilling vessel in a fixed location above the well being drilled in the ocean floor.

In some marine locations, the wave action is rather severe-frequently being as much as to feet or more. This causes various problems. One of the bigger difficulties is in the transfer of personnel and material or equipment from a cargo vessel to the working deck of the drilling platform. If the cargo vessel, for example, is anchored next to a fixed platform, the anchored vessel moves up and down While the fixed platform is stationary. This movement can cause severe damage to equipment or endanger the lives of personnel being transferred. Simi- 3,398,845 Patented Aug. 27, 1968 lar difiiculties are encountered when transferring equipment and personnel between a cargo vessel and a floating drilling platform because here the cargo vessel and the floating drilling platform seldom, if ever, move up and down in unison; in fact, frequently one is moving down while one is moving up, which compounds the difilculties.

Considerable work has been done toward trying to develop means for the safe transfer of equipment and personnel. For example, various servo and sensing systems have been devised to maintain cargo a set or constant approach or departure distance above the deck of the cargo vessel when the cargo is being raised or lowered, and to gradually change this set distance. This system, while showing promise, is rather complicated and costly and may well be limited in size by economics.

From the above brief description of the problem, it is seen that there is a need for a simple yet effective system to effect the transfer of equipment and personnel between a cargo vessel and a working drilling platform. Applicant invention provides just such a system. Various objects and a better understanding of the invention can be had from the following discussion taken in conjunction with the drawings in which:

FIGURE 1 illustrates a transfer line and a fixed platform system;

FIGURE 2 illustrates a bow view of a cargo vessel provided with a swivel fork extended above its superstructure;

FIGURE 3 is a side view of such cargo vessel having a swivel fork;

FIGURE 4 is a side view showing the fork of the vessel of FIGURES 2 and 3 in engagement with the transfer line of FIGURE 1;

FIGURE 5 is a plan view of FIGURE 4; and

FIGURE 6 is a view of a floating drilling platform and its associated transfer line.

Attention is first directed to FIGURE 1 which illustrates the transfer line and its anchorage. Shown thereon is a working platform or deck 10 supported above a body of water 12 by structure 14 which is illustrated as being piles driven into the bottom 16 beneath the body of water. Shown on top of deck 10 is a drilling derrick 18 which is used for normal drilling operations, for example.

A transfer line 20 is connected between an anchor 22, which is set in the ocean bed 16, and the working deck. This line 20 is illustrated as extending over derrick 18 and is secured at 24 to the working platform.

The complementary part of the transfer system of FIG- URE 1 is illustrated in FIGURES 2 and 3 which show a cargo vessel which has been especially modified. Shown in FIGURES 2 and 3 is a cargo ship 26 having a superstructure or pilot house 28. Above the pilot house is a special modification. This includes a swivel fork 30 which has an upright member and two prongs forming a cradle at 32. This swivel fork system 30 must be rather strong as it must hold the transfer line taut and thus support the weight of the cargo being transferred. Referring back to FIGURE 1, line 20 must be sufficiently high so that it can be placed in cradle 32 of swivel fork means 30. It is preferred that at a distance /2 the length of vessel 26 from platform 14 that line 20 be at least as high as the swivel fork 30. However, if it is not quite this high it may be possible to pick up transfer line 20 and place it in cradle 32 provided there is sufficient slack. Ordinarily, it is desired that anchor 22 be set from about 2,000 to 5,000 feet from the fixed platform 10. Ordinarily, this distance is from about 8 to 16 times the depth of the Water where the platform is located.

When it is desired to transfer material between the cargo vessel in FIGURES 2 and 3 and the working deck 10 of FIGURE 1, vessel 26 is ordinarily maneuvered adjacent platform 10 such that cradle 32 can pick up transfer line 20. Vessel 26 is then moved outwardly along line until sufficient contact force is picked up between the transfer line and the fork means so that the transfer line is held in firm contact with the fork. A typical position of the ship is now illustrated in FIGURES 4 and 5. In FIGURE 4, for example, it is seen that the section 20A of transfer line 20 between fork 30 and derrick 18 is held in tension high above the surface 34 of the body of Water 12. The cargo is then lifted from the deck of vessel 26 by the hoist line 27 of traveling block 36 and transferred along transfer line segment 20A by means of a traveling block 36, traveling along this transfer line. The minimum distance of cargo vessel 26 of FIGURE 4 from platform 10 is preferably about three lengths of the cargo vessel.

The traveling block 36 conveying cargo 25 between the platform 10 and the cargo vessel 26 can then be moved easily in a known manner between the two. Loading or unloading from the traveling block 36 to platform 10 when the traveling block 36 reaches derrick 18 is no problem since both the platform and the traveling block are stationary. The movement of line 20A at derrick 18 is essentially nil. If the sea is rough, cargo vessel 26 may be moving up and down with the waves. However, this presents no problem as the distance between the overhead line 20A adjacent to fork means 30 and the deck of the cargo ship 26 is constant. As these are fixed, then movement of the vessel 26 up and down will be closely followed by a similar movement of the cargo 25 being transferred and the cargo 25 will move away or move toward the deck of vessel 26 in a steady or controlled manner and there should be no hard bumping between the two. Roll of cargo vessel 26 may, in some cases, present some difliculties; however, this can be minimized by heading the cargo vessel 26 directly into the seas, i.e., perpendicular to the oncoming waves. As shown in plan view of FIG- URE 5, the vessel 26 can -be moved to any directional position, as necessary, as indicated by dotted outline 26A. Shifting the heading of vessel 26 also facilitates picking up cargo from any place on the deck of the vessel.

As mentioned above, the search for petroleum is being made in deeper and deeper waters, and it is now common to support the drilling equipment on a floating vessel itself. A system of transferring equipment and personnel from a floating cargo vessel to a floating drilling platform is illustrated in FIGURE 6. Shown in FIGURE 6 is a floating platform 40, which may be of any varied type or shape, in which the deck 42 is supported above the surface 34 of the body of water 12. Supported above platform or deck 42 is a derrick 44. Platform 42 is maintained in a relatively fixed position over a spot on the floor of body of water 12 where it is desired to drill. Various means for maintaining this drilling barge in position are known. It is illustrated in FIGURE 6 as being anchored to anchor means 46 by lines 48. These lines are ordinarily attached to the lower side of the floating deck 42 or the substructure.

I shall now discuss the transfer line of the embodiment of FIGURE 6. The transfer line 50 extends from first anchor means 52 on one side of the floating drilling barge to second anchor means 54 on the opposite side thereof. Line 50 is continuous from anchor means 52 to 54 and extends over derrick 44 in a movable contact therewith. As platform is floating, this arrangement will eliminate side pull on such floating drilling vessel due to tension in the cargo line when cargo is being loaded or unloaded from the floating platform. The loading and unloading of material from the floating platform 42 is essentially the same as that described in connection with the fixed platform. Briefly, vessel 26 is moved so that cradle 32 or fork means 30 engages line adjacent the floating platform. Then the floating cargo vessel 20 is moved outwardly along line 50 until suflicient contact force is picked up between the transfer line and the fork so that the line is held in firm contact. Thereafter, objects are transferred between the floating platform 42 and the floating cargo vessel 26. The same precautions as described above can be taken to minimize roll.

Although a limited number of embodiments of the present invention have been shown, various modifications can be made thereto without departing from the spirit or scope of the invention.

I claim:

1. A method of transferring objects between a floating vessel having a swivel fork means supported above its superstructure and a working platform supported above the body of Water and having a transfer line connected to anchor means, which comprises:

maneuvering said floating vessel under said transfer line adjacent said working platform so that said swivel fork means engages said transfer line; moving said floating vessel outwardly from said working platform until suflicient contact force is picked up between the transfer line and the fork means so that the transfer line is held in firm contact with the fork; and

thereafter transferring objects between said working platform and said floating vessel along said transfer line.

2. A method as defined in claim 1 including the step of heading the bow of said floating vessel perpendicular to the oncoming waves. 

